NT System Drive failing in Raid1 array

I have two drives in a raid1 array, one is bay 0 and one in slot 1. The drive in bay 0 is failing threshold tests, and CIM is telling me to replace it. The problem is that it is the NT system disk, and if I remove it, NT will not boot. I can get around that by creating a boot floppy and pointing the boot.ini at the correct boot disk.

The problem is that the spare drive that is there has been take out of a decomissioned server, and I don't know what is on it. How would I put it in to the array without it writing it's contents over the second disk in my array.